load(BREAKING)!: improve load options

[Kybxd]

Field Mode in load.BaseOptions is redefined:

• BREAKING: Mode LoadMode -> Mode *LoadMode
• BREAKING: load.Paths and load.PatchPaths are removed. Use load.WithMessagerOptions instead.
• load.modeNone is removed from load.LoadMode
• load.LoadMessagerInDir and load.LoadMessager can accept nil *load.MessagerOptions now.

[codecov]

Codecov Report

❌ Patch coverage is 80.72289% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.36%. Comparing base (a00850e) to head (94da109).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
load/options.go	74.50%	9 Missing and 4 partials ⚠️
load/load.go	90.62%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #287      +/-   ##
==========================================
- Coverage   71.42%   71.36%   -0.06%     
==========================================
  Files          84       84              
  Lines       10334    10358      +24     
==========================================
+ Hits         7381     7392      +11     
- Misses       2388     2397       +9     
- Partials      565      569       +4     

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[wenchy]

Maybe there is no need to change naming, as it is already in load package:

• Options-> LoadOptions
• Option -> LoadOption

[Kybxd]

Keep consistent with cpp implementations is better for subsequent maintenance.

[wenchy]

As MessagerOptions is also load options only for messager-level. For consistency, should we also rename it to LoadMessagerOptions just like Options renamed to LoadOptions?

• Options-> LoadOptions
• MessagerOptions-> LoadMessagerOptions

A better solution can be considered. C++ or other programming languages can use load namespace:

For example:

namespace load {

struct Options {
  ...
}

struct MessagerOptions {
  ...
}

} // namespace load